JPS6323166A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To obtain an economical toner superior in fluidity and triboelectrification characteristics by mixing thermoplastic resin core particles having an average particle diameter of 1-15mum, with a colorant alone, or together with other necessary fine additives, and applying mechanical stress in such conditions as forming an average particle diameter of 1-20mum. CONSTITUTION:The thermoplastic resin core particles having an average particle diameter of 1-15mum are mixed with the colorant alone, or together with other necessary fine additives, and subjected to mechanical stress in such conditions as forming an average particle diameter of 1-20mum, while care is taken lest the resin core particles be melted and attached to each other to form coase agglomerates, or be too finely pulverized by too strong stress, but it is necessary that the colorant powder is attached to the surface of each resin particle and buried into the surface in a state of primary fine particles. It is preferred to control the toner particle size to the range of average particle diameter of 1-20mum and to substantially eliminate the toner particles of <=0.5mum and >=25mum diameters.

Description

DETAILED DESCRIPTION OF THE INVENTION [Statement of the Invention] (Field of Industrial Application) The present invention relates to a toner for dry developing electrostatic latent images such as those used in electrophotography.

(Prior Art) Conventionally, dry developing methods include a method using a two-component developer in which toner particles are mixed with carrier particles, that is, glass beads or magnetic powder, and a method in which a two-component developer is used in which toner particles are mixed with carrier particles, that is, glass beads or magnetic powder. There is a method using component toner.

Furthermore, recently, a method using a non-magnetic one-component toner with excellent environmental resistance has been proposed.

Conventional methods for manufacturing these toners include thermoplastic resins, colorants such as pigments and dyes, waxes, plasticizers,
Additives such as charge control agents are heated and melted, secondary agglomerated pigments are kneaded by applying strong shearing force, and if necessary, magnetic powder is heated and melted to form a uniform composition.

Most of the methods involved pulverizing the material after cooling and classifying it into 9 classes.

However, in terms of quality, the toner obtained by this pulverization method has different toner particle sizes and shapes, and is generally amorphous, so each has different triboelectric charging characteristics, which can cause scumming or scattering inside the machine. Next door.

Another disadvantage is that the toner has poor fluidity, making it difficult to replenish and causing trouble.

Improvements are desired. In addition, from the viewpoint of the manufacturing process, there are problems such as the kneading process requires a large amount of energy and the number of man-hours is large because one classification is required.

To this end, attempts have been made to obtain a 9-spherical toner by a spray drying method and by suspension polymerization.

However, in the former case, it is necessary to select a resin with good solubility in the solution, and there remains a problem with the offset phenomenon to the fixing drum, and in the latter case, problems with blocking and offset phenomena remain. It has not been industrialized.

In addition, conventional toners are disadvantageous in terms of cost because colorants and charge control agents, which are relatively expensive raw materials for toners that inherently exhibit characteristics on the toner surface, are also contained deep within the toner.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned problems, and the shape of the nine particles is rounded (rounded) compared to conventional toner.
The object of the present invention is to provide a toner which has relatively uniform particle sizes, has excellent fluidity and triboelectric charging properties, and is economically advantageous.

[Structure of the invention]

(Means for solving the problem) As a result of extensive research, the present inventors found that the average particle size is 1 to 15.
μ thermoplastic resin core particles (A) and two colorants (B) alone, or colorant (B) and other necessary fine particles,
Mix by applying mechanical strain under conditions such that the average particle size is in the range of 1 to 20μ, and embed the colorant (B) and other necessary fine particles as substantially primary particles inside the core particles (A). The present invention provides an electrophotographic toner.

9 In this specification, the particle size is measured using a Coulter counter TAU type (manufactured by Coulter Electronics).
is shown on a 1 volume basis.

The resin used in the present invention is as follows.

Polystyrene, styrene-containing copolymers of styrene and acrylic ester, methacrylic ester, acrylonitrile or maleic ester, polyacrylic ester, polymethacrylic ester, polyester, polyamide, polyvinyl acetate type, epoxy resin, phenolic resin.

Hydrocarbon Resin 1 Examples of binder resins known per se include petroleum resins and chlorinated paraffin, and these may be used alone or in combination.

In the present invention, there are no particular limitations on the means for preparing thermoplastic resin core particles (A) with an average particle size of 1 to 15 μm, and examples include: (1) crushing/classification, (2) suspension polymerization, (2) dissolution/precipitation, (2) spraying. Various methods such as can be applied.

In addition to the magnetic powder described below, the thermoplastic resin core particles (A) contain a lubricant such as wax, a fluidity imparting agent such as colloidal silica, and a charge control agent.

Low molecular weight polyolefins and the like can be used in combination depending on the purpose, and if they are fine particles, they can be embedded in the same manner as the colorant (B). This operation can be performed simultaneously with, or before or after embedding the colorant (B), depending on the purpose. Also.

It is preferable that these thermoplastic resin core particles (A) are substantially free of particles of 25 μm or more, since particles of 25 μm or more are not preferable for toners, as will be described later.

Various pigments and dyes can be used as the colorant (B), and although it is not necessarily limited to these, examples include the following.

Yellow pigment/dye zinc yellow, yellow iron oxide, Hansa Yellow, Disazo Yellow,
Quinoline yellow, permanent yellow.

Red pigment/dye Red Garla, Permanent Red, Lysol Red, Pyrazolone Red, Watchsen Red Ca salt, Watchen Red Mn salt, Shikiresodo C, Lake Left D, Brilliant Carmine 6B, Brilliant Carmine 3B.

Blue pigment/dye Navy blue, phthalocyanine blue, metal-free phthalocyanine.

In addition, if necessary, colored pigments such as orange, purple, and green, titanium oxide, and oil blanks.

White or black pigments or dyes such as carbon black can be used.

In the present invention, the method of mixing the thermoplastic resin core particles (A) and the colorant (B) by applying mechanical strain under conditions such that the average particle size is in the range of 1 to 20 μm is as follows:
The conditions are such that the thermoplastic resin core particles (A) are not fused into large lumps, or conversely, the strain force is too large and the resin particles (A) are not pulverized into fine particles. The conditions are such that the colorant (B) adheres to the surface and is embedded in the state of primary particles. As a specific method that satisfies both of these conditions, a mortar is used in the laboratory. Industrially,
The operating conditions of a dispersing machine such as an attritor, a ball mill, or a sand mill, which exhibits the same effect as a mortar, and the conditions of a dispersion medium with a throughput of 1 may be changed so as to achieve the above objective.

However, in a mortar, it takes several hours to several tens of days, and in a ball mill or sand mill, it takes a long time, so industrially, powder is mixed in a fluidized bed state, with a mixer in which the powder moves at high speed with air current, or in an impact mill. It is a mixer that is equipped with blades, hammers, etc. that give

An example of such a mixer is the SI Mill (manufactured by Toyo Ink Manufacturing Co., Ltd., see Japanese Patent Publication No. 57-43051 for an overview).
, Atomizer-9 free crusher (Nara Kikai Seisakusho), Kawasaki Heavy Industries ■ crusher (KTM-1), and the like.

These devices can be used as they are or modified as appropriate to meet the purpose of the present invention. If possible, use a closed system device, such as a hyperdizer (■
Nara Kikai Seisakusho) is preferable.

Through such mixing treatment, thermoplastic resin core particles (A
) The effect that the colorant (B) adheres to the inside of the core particles and embeds them in the state of primary particles occurs because the core particles (A)
And the colorant (B) is powder to powder or two walls.

It collides with a dispersion medium such as beads, causing instantaneous and one-time damage.
It is thought that a phenomenon similar to a mechanochemical reaction in the field of inorganic chemistry is occurring as the temperature becomes quite high in some parts, and the air flow temperature in the system rises to near the Tg of the resin, causing the system to cool down. In some cases, it may be necessary.

The above phenomenon can be understood by observing electron micrographs before and after premixing. That is, before the mixing treatment, the core particles (A) and the first colorant (B), which have a relatively large particle size distribution, are in a partially aggregated state.

After the treatment, the surface of the thermoplastic resin core particle (A) is smooth, and almost no fine particles of the colorant (B) can be seen.
Covered with a thin layer of resin, the particles remain unbreakable even during running tests inside a copying machine. Therefore, as will be described later, even when the charge control agent is subjected to the same treatment as the colorant (B), it can be easily adhered to or embedded in multiple layers on the surface.

Effective control can be achieved with a small amount of charge control agent.

Furthermore, according to the measurement of particle size distribution, it is recognized that the average particle size has increased by about 20% after the mixing treatment.

By such a mixing process, the first colorant (B) is embedded inside the thermoplastic resin core particles (A) and becomes substantially primary particles. -The fact that the toner particles are powder-like particles is almost the same as that of toners that have gone through a thorough kneading process using conventional methods, and the color density of images obtained using these toners is the same. It is confirmed.

Further, it is observed that the thermoplastic resin core particles (A) after the treatment have fewer small particles, have a uniform particle size, and have rounded corners of nine particles. That is, it is considered that the core particles (A) having a small particle size are sized into particles of a constant size by the mixing process.

There are two possible factors to achieve the above effects, but according to research by the present inventors, the speed of the airflow is the highest, and is preferably several tens of meters/second to several hundred meters/second.

In the present invention, the particle size of the toner is as follows.

It is preferable that the average particle size is in the range of 1 μm to 20 μm, and substantially no toner with a particle size of 0.5 μm or less and 25 μm or more is contained. If a large amount of toner with a particle size of 0.5 μm or less is fed, fluidity deteriorates and background smear occurs. Furthermore, if the amount of toner larger than 25μ increases, one image will be distorted and the commercial value will be reduced.

In the present invention, when preparing a -component magnetic toner, magnetic powder is used as thermoplastic resin core particles mixed with resin in advance,
The average particle size may be 1 to 15μ, or magnetic powder may be embedded in the thermoplastic resin core particles (A) by the same operation as the colorant (B) in the present invention. There are no particular restrictions on what can be used as the powder, but when using the latter method, it is preferable to use fine magnetic powder with an average particle size of 1μ or less, preferably 0.2μ, and various types of ferrite, magnetite, hematite, etc. of iron, zinc and cobalt.

Per se known materials such as alloys or compounds of nickel, manganese, etc. can be used, and depending on the purpose, these magnetic powders may be classified or subjected to per se known surface treatment.

For example, it may be subjected to hydrophobic treatment or silane coupling agent treatment.

The charge control agents used in the present invention are known per se, and include dyes such as Fetschwarz HBN, Nigrosine Base, Friliant Schwarz, Zabon Schwarz X, Ceres Schwarz RG, and other metal-containing dyes. C, 1, Solvent Black 1゜2.3,5
,7. C, 1, acid black 123.22.2
3.28.42,43. Oil black (C, 1,
26150), dyes such as spirone black, naphthenic acid metal salts, fatty acid metal soaps, etc.

Since the purpose of the charge control agent is to control the surface charge of the toner, the charge control agent is used together with the colorant (B) or in combination with the colorant (B).
) It is preferable that the mixture be attached to or embedded in the toner by a similar operation after the mixing treatment.

The present invention will be explained below using specific examples. The middle part of the example shows parts by weight.

Example 1 Styrene-acrylic resin (manufactured by Sanyo Chemical Co., Ltd.).

In a Henschel mixer, 88 parts of Hymer SBM-73 (trade name), 4 parts of a charge control agent (manufactured by Orient Chemical ■, trade name Pontron S-34), and 3 parts of low molecular weight polypropylene (manufactured by Sanyo Chemical ■, trade name Vinicol 550P) were added. This is premixed, melted and kneaded using a two-wheeled extruder, allowed to cool, and this kneaded material is roughly crushed using a 1-set chef's mill with an upper limit particle size of 25μ or less and an average particle size of about 10μ.
Core particles (A1) were prepared.

100 parts of the core particles (AI) and 5 parts of carbon black were preliminarily mixed in a super mixer at a rotation speed of 250 rpm for 1 minute.

Carbon black was electrostatically attached to the surface of the core particles (A1). Next, this was introduced into Free Mill M-3,
The internal rotation speed was 500 rpm. At this time, the airflow velocity in the free mill was about 90 m/sec, and the average residence time of the introduced mixture in the system was about 3 seconds.

The mixture discharged to the collector was passed through a free mill seven times in total to obtain the desired toner.

The average particle size of this toner particle was 12μ.

There were substantially no particles smaller than 5μ and particles larger than 25μ and no two-classification was required.

80 parts of this toner and 720 parts of iron powder carrier (manufactured by Dowa Iron Powder ■, trade name: DSP 128B) were mixed in a ball mill for one hour to prepare a two-component developer, which was then transferred to a commercially available copying machine (Sanda Kogyo side). The sample was set in a mold (trade name: DC-232), and copies were made continuously on plain paper using a test chart.

In this copying, the fixing properties, charge stability, anti-blocking properties, and anti-offset properties of the toner were extremely good, and the toner of the present invention was poured into the toner replenishment hof bar in the copying machine.

In the running image test carried out, the images maintained are the same as the initial images after 60,000 images.

The replenishment of toner was also good.

Example 2 Thermoplastic resin core particles (A2) were prepared in the same manner as in Example 1, except that the charge control agent was not added during the preparation of the thermoplastic resin core particles (A1). This core particle (
Using 100 parts of A2), 4 parts of carbon black, and 2 parts of the same charge control agent as in Example 1, a toner was obtained in the same manner as in Example 1, and this toner was subjected to the same tests as in Example 1. The image was clear, and the toner had very good charge stability, blocking resistance, and offset resistance. Further, although the fixability of this toner was slightly reduced, it did not affect the copied image, and results equivalent to those of Example 1 were obtained in the running test.

Example 3 In Example 1, a red organic pigment (IIkL28 Lionol Red) was used instead of carbon black.

A toner was obtained using the same procedure except that Toyo Ink Seisakusho (product name) was used, and the same test was conducted, and it showed excellent effects. When used, the phenomenon of pigment filming on the photoreceptor, which is often a problem, has been a problem.

Comparative Example 1 Using the same raw materials as in Example 3, production was carried out by a conventional method. That is, mix each raw material.

After pre-mixing with a Henschel mixer, this is melted and kneaded with a two-wheeled extruder, allowed to cool, and this kneaded material is coarsely crushed using a type jet mill with an upper limit particle size of 25.
A toner with an average particle size of about 12 μm or less, and a toner of 5 μm or less was obtained.

When this toner was subjected to the same test as in Example 1, it was found that when compared with the toner of the present invention, slight fading was observed in the solid areas, and a running test revealed that the image density decreased after approximately 5,000 copies. A filming phenomenon of red pigment on the photoreceptor occurred, and a bridging phenomenon was observed in the replenishment hopper.

Example 4 53 parts of styrene-acrylic resin (manufactured by Nippon Carbide Industries, trade name: Nikalide-NC-6100), 2 parts of charge control agent (manufactured by Orient Chemical, trade name: Bontron E-81)
1 part, 3 parts of low molecular weight polypropylene (manufactured by Sanyo Kasei ■, trade name Vinicol 550P), and 40 parts of magnetite (Toda Kogyo's type, trade name EPT-500) were prepared in the same manner as in Example 1 until the average particle size was approximately Core particles with a diameter of 10μ (A3
) was prepared.

98 parts of this core particle (A3) and 2 parts of carbon black were pre-mixed in a super mixer at a rotation speed of 280 Qrpm for 1 minute, and four people placed this in a closed system atomizer to rotate the internal rotating blades. The speed was 4500 rpm. The airflow velocity at this time was 80 m/sec.

The introduced mixture was allowed to stay for 30 seconds and then discharged into a Sankron collection to obtain a toner.

The average particle size of this toner was 12.5 μm, and no particles of 5 μm or less and 25 μm or more were measured.

200g of this magnetic toner was transferred to a commercially available copier (Canon).
The test chart was set in a developing machine (NP-500+Canon (trade name)) and a clear image was obtained by copying the test chart onto plain paper.

Toner fixability, charge stability and profking resistance,
The offset resistance was extremely good, and when a running test was performed while adding toner, images equivalent to the initial image were obtained over 50,000 sheets, and no toner bridging phenomenon was observed.

Comparative Example 2 Using the same raw materials as in Example 4, a one-component magnetic toner was obtained by a conventional method. That is, each raw material is premixed with a Henschel mixer, melted and kneaded with a twin-screw extruder, allowed to cool, coarsely pulverized with a cutting mill, first finely pulverized with a jet mill, and then pulverized to 5 μm with an Alpine classifier. Average particle size: 13μ, excluding the following fine powders and particles larger than 25μ
I got the toner.

When the same test as in Example 4 was conducted using this toner, the image density decreased after about 10,000 sheets, background smear occurred, and a bridging phenomenon was observed in the hopper.

Example 5 In Example 1, instead of styrene-acrylic resin,
Polyester resin (@Kako Co., Ltd.)

A toner obtained in the same manner except that KTR-2500 (trade name) was used showed similar good suitability.

(Effects of the Invention) The electrophotographic toner according to the present invention has particles without corners and a surface that is hard to break.

Furthermore, since the particle size is relatively uniform, it has excellent fluidity and charge stability, and exhibits good characteristics even in long-term running tests. Also.

Because of this characteristic, it is an excellent toner that is compatible with developing devices that use non-magnetic one-component toners, such as the one disclosed in Japanese Patent Application Laid-Open No. 60-22150, where conventional toners had various problems. be.

Furthermore, it is simpler to manufacture than conventional methods and is advantageous in terms of cost.

Claims (1)

[Claims] 1. Thermoplastic resin core particles (A) with an average particle size of 1 to 15 μm
The colorant (B) alone, or the colorant (B) and other necessary fine particles are mixed by applying mechanical strain under conditions such that the average particle size is in the range of 1 to 20μ. B
) An electrophotographic toner comprising other necessary fine particles substantially as primary particles embedded inside core particles (A). 2. Thermoplastic resin core particles containing fine magnetic powder (A
), and the non-magnetic single-component toner according to claim 1, which contains no magnetic powder.